Leukocytes are important for research and are utilized in various medical and medical diagnostic applications. Problems occur when it is necessary or desired to snip leukocytes from one location to another. Generally, leukocytes heretofore had been shipped cold, e.g., about 4.degree. C., because they are unstable at warmer temperatures such as room temperatures unless used within five to six hours of their separation from whole blood.
Methods of collecting blood from donors or patients and separating leukocytes therefrom have been, until the invention described herein, unsatisfactory for forming suspensions of leukocytes or specific fractions thereof which are stable at room temperature for extended periods. The usual method is to collect or place the blood into a syringe or container containing sufficient heparin to prevent clotting, separate the leukocytes and suspend them in a buffered medium. Another method comprises collecting blood, defibrinating it with glass beads and separating the granulocytes by magnetic particles to leave the lymphocytes in the supernatant. Still another technique comprises placing collected blood in Hank's solution containing sufficient heparin to provide 30 units/ml. of blood. This latter method is about half as effective in maintaining viability compared to drawing blood directly into BSS- or MEM-heparin solution as in the invention described herein.
The above and other known methods of separating leukocytes from blood do not result in a suspension of leukocytes which can be shipped from one location to another at temperatures substantially above 4.degree. C., e.g., room temperature. There is thus a need for a stable suspension of leukocytes which can be shipped at temperatures which may vary from about 4.degree. C. to about 30.degree. C. and still remain viable for several days.